1. Field of the Inventions
The present invention relates to an exhaust nozzle for a ducted fan unit for a model aircraft which includes a fan, a motor and an exhaust duct with an end opening and more particularly to a variably convergent exhaust nozzle which provides not only maximum thrust, but which also may be adjusted for providing maximum speed.
2. Description of the Prior Art
U.S. Pat. No. 4,685,289, entitled Power Plant for Model Jet Aircraft, issued to Lee W. Anderson and Robert S. Violett on Aug. 11, 1987, teaches a ducted fan unit for use in a power plant of a model vehicle, such as either a model aircraft or a model boat. The ducted fan unit includes a motor which is a one cylinder internal combustion engine, an exhaust duct with an end opening, a fan and a mounting for the motor. The one cylinder internal combustion engine utilizes a special vertically oriented carburetor. The exhaust duct is supported by a set of stators each of which has an aerodynamic shape for straightening airflow through the exhaust duct. The fan has seven identical individual replaceable blades. The fan is disposed at the front of the exhaust duct and is directly driven by the motor. One stator is essentially encloses the vertical carburetor and smoothly directs the airflow from the fan around the carburetor to the one cylinder of the motor for cooling. The stator has an opening to the carburetor air inlet for providing air under pressure thereto. The stator is shaped to cooperate with the exhaust duct and aft fairings of the power plant in order to deliver a smooth airstream which has a uniform non-turbulent flow in order to produce a maximum propulsive efficiency.
U.S. Pat. No. 4,307,857, entitled Ducted Fan Unit, issued to Byron L. Godbersen on Dec. 29, 1981, teaches a ducted fan unit which is installed in a scale model airplane. The ducted fan unit is positioned centrally within the hollowed fuselage and includes an engine and a fan which is assembled thereto. The ducted fan unit is secured to a mounting bracket which is aerodynamically sleek. The mounting bracket is secured to a cowl and positions the fan within the forward portion of the cowl. The rearward portion of the cowl includes a flow straightener which has radially disposed spokes with curved forward portions to deflect the air flow linearly.
U.S. Pat. No. 4,250,658, entitled Ducted Fan for Model Aircraft, issued to Robert W. Kress on Feb. 17, 1981, teaches a ducted fan unit for a model aircraft which is powered by a piston engine. The piston engine is mounted in a hollow portion of an inner core body and drives a multibladed fan. Two sets of stationary vanes are attached to the core body. A cylindrical shroud, which is fitted over the assembly, is attached to the outer ends of the vanes.
U.S. Pat. No. 3,434,679, entitled Simulated Reaction Engine Model, issued to John R. Erwin and John T. Kutney on Mar. 25, 1969, teaches a model ducted fan unit which simulates the in-flight aerodynamic characteristics of a ducted fan unit which is powered by a turbojet engine. The model ducted fan unit has an external configuration which is similar to the engine simulated and includes a fan and a turbine engine. The fan is disposed within an annular casing and the turbine engine drives the fan. The external configuration of the model ducted fan unit is sized in predetermined reduced lineal scale to the engine simulated and the fan and turbine engine are sized to develop a pressure ratio across the fan substantially similar to the pressure ratio across the simulated turbine engine fan and a mass flow rate reduced in relation to the mass flow rate of the simulated engine by substantially the square of the predetermined reduced lineal scale.
U.S. Pat. No. 3,612,400 entitled Variable Jet Propulsion Nozzle, issued to Douglas Johnson and Henry M. Mar on Oct. 12, 1971, teaches an exhaust duct and variably convergent-divergent propulsion nozzle for a supersonic turbofan engine. The nozzle includes a ring of leaves providing a convergent nozzle portion and a second ring of leaves downstream of the first defining a divergent nozzle portion. The downstream end of the divergent nozzle portion is connected to a ring of leaves defining a fairing around the nozzle. The fairing and divergent leaves are free to float radially at their downstream ends. The converging nozzle leaves and the forward end of the diverging nozzle leaves are actuated by a common linkage so as to coordinate the movement of the two and permit the floating movement of the downstream end of the nozzle. The structure, including the exhaust duct wall, is characterized by lightweight construction and arrangements for cooling the structure exposed to hot gas. Outward movement of the fairing leaves is limited by a ring of swinging links which includes a stop which limits their extending motion to a degree short of straightening the joints.
U.S. Pat. No. 4,603,568, entitled Method of Fabricating Bimetal Variable Exhaust Nozzle Flaps and Seals, issued to Melvin R. Jackson, Stephen F. Rutkowski and Paul A. Siemers on May 30, 1985, teaches a method of forming a generally planar part for a jet engine. The part can withstand high thermal stress but not high mechanical stress. A preformed strip of a superalloy is mounted around a drum shaped mandrel. A low pressure plasma deposit of a different superalloy is formed on the preformed strip. The strip is demounted and mechanically straightened.
U.S. Pat. No. 4,638,946, entitled Variable Configuration Exhaust Discharge Opening for a Jet Propulsion Engine, issued to John M. Hall on Jan. 27, 1987, teaches a gas turbine jet propulsion engine which has a rectangular exhaust gas outlet. A pair of u-shaped tracks one on each side of the outlet and which extend downstream of it, support rollers carrying the plates. Of a pair of articulated deflectors one above and one below the outlet. The deflectors are translatable along the tracks between the final exhaust discharge opening of the engine. The configurations include a convergent divergent nozzle, a thrust vectoring nozzle and thrust reversing outlets.
U.S. Pat. No. D-241,360, entitled Toy Jet Engine, issued to James J. Scozzafava on Sept. 7, 1976, teaches a design for a ducted fan unit for a model jet aircraft.
U.S. Pat. No. 4,573,937, entitled Jet Propelled Model Airplane, issued to Victor Stanzel on Mar. 4, 1986, teaches a line-controlled, centrifugal fan, jet-propelled model airplane in which the impeller of a fan is contained within the fuselage of the aircraft. The impeller of the fan is driven from a remote drive unit by an elongated flexible cable which is contained within a flexible sheath. The impeller rotates about an axis perpendicular to the longitudinal axis of the aircraft and is driven in a direction of rotation tending to rotate the aircraft about its lateral axis in a noseup direction, due to the frictional contact of the compressed air between the rotating impeller and the housing of the centrifugal fan mounted within the fuselage. A flywheel which is powered by the electric motor in the remote drive unit controls the rate of acceleration and deceleration of the aircraft as an electric motor in the drive unit is switched on and off.
U.S. Pat. No. 4,369,149, entitled Carburetor for Model Jet Power Plant; Having Circular Duct and Multibladed Fan, issued to Robert S. Violett on Jan. 18, 1983, teaches a vertically oriented carburetor for use in a model jet aircraft power plant which includes a circular duct and a multibladed fan. The carburetor utilizes an essentially cylindrical body which has a web portion to permit air flow from the fan for cooling the cylinder of a model engine and a forwardly oriented carburetor air opening for receiving pressurized air from the fan. Concentric fuel feed and throttle tubes have their adjustments for control at the top end so as to be external to the power plant circular duct to eliminate interference with the propulsion air stream from the fan.